This invention relates to the field of drain apparatus for emptying sanitary holding tanks installed in recreational vehicles and travel trailers. Such vehicles contain toilets and other sources of sanitary sewage; being mobile, the collected sewage is stored in holding tanks which must be emptied periodically. Most Recreational Vehicle parking facilities, trailer parks and many on road servicing establishments have suitable sewage dump station facilities, usually in the form of a ground level connection into which sewage may flow or be pumped.
Since the holding tank on a Recreational Vehicle must be located at a lowest point on the vehicle for gravity flow of sewage, the drain is similarly low. Thus the drop from vehicle drain to sewage dump station is quite small. This results in puddling and trapping of sewage in lines draining from the vehicle. In consequence, there is spillage of sewage, and contamination which is difficult to clean.
This has led to the abandonment of flexible bellows tubing as a drain line, and the adoption of various structures in an attempt to obtain a suitable drain apparatus.
U.S. Pat. No. 2,915,081 to Warren discloses a permanently affixed telescoping drain showing a construction in which each successive pipe section is larger than its preceding section. Both ends of the pipe are rigid, and the connection to the trailer is a pivoting joint. The device is suspended below the trailer. Seals and locknuts are described to hold the telescoping sections together. This unit is most similar to the telescoping device shown in the sales catalog you disclosed.
U.S. Pat. No. 4,133,347 to Mercer discloses a removable drain in which a bellows tube is held in a rigid tube. This patent clearly discloses the use of the standard removable fittings on each end of the drain to fit to standard trailer and sewage dump station connections. The actual drain tubing is the known bellows extensible tubing.
U.S. Pat. No. 4,854,349 to Foreman discloses a fixed tubing section, permanently affixed to the underside of the camper, and containing an extensible bellows tube for connection to a sanitary sewage dump station.
U.S. Pat. No. 3,623,500 to Hoy discloses a semicircular conduit for supporting a bellows drain line to prevent sag and to guide the drain line.
U.S. Pat. No. 5,023,959 to Mercer (the inventor in the '347 patent above) discloses a motorized system for extending a bellows drain tube and then for pulling back on the bellows once it is connected to the sewer pump out to reduce sag.
U.S. Pat. No. 4,844,121 to Duke discloses a drain line which is attachable to a trailer drain outlet, and which has a series of rigid telescoping tubes. The tubes nest, smaller inner tube nearer the trainer; the tubes are locked together with a compression nut. Rigid inlet and outlet connectors are shown, and a washout connection for a water hose is provided on the inlet connector. Standard interconnects are shown (FIG. 4, item 50).
U.S. Pat. No. 4,779,650 to Sargent et al. shows a rigid telescoping tube drain, permanently affixed to the trailer. This patent shows a bellows outer covering which seals the sliding joints, but the device is a continuous telescoping rigid tubing construction, including rigid rotating joints at the trailer end.
U.S. Pat. No. 5,141,017 to Trottier shows a fitting for connecting a drain to a trailer sanitary system with a hose connection and valve for back flushing the line. This design is an improvement over the flush shown in Mercer '347 as it permits blockages in the dump valve to be cleared as well as cleaning the line after dumping.
U.S. Pat. No. 3,496,959 to Wolfe is a early design for a telescoping drain tube made of rigid sections.
U.S. Pat. No. 2,514,230 to Feazel is an earlier patent showing a vehicle drain.
The current art is permanently mounted rigid plastic telescoping lines affixed to the trailer holding tank through a ball joint and valve. These lines are, of necessity, the lowest mounted portions of the Recreational Vehicle or trailer. They are invariably made of plastic, to avoid corrosion and failure, and are therefore fragile. Any damage to these lines as by impact or thrown road debris, can breach the integrity of the entire sewage holding system, rendering the entire toilet and drain system in the Recreational Vehicle unusable. Such accidents can equally result in major sewage spills and contamination.